Clinical Profile and Dynamic Magnetic Resonance Imaging in Hirayama Disease: a Single-Centered Cross-Sectional Study in Nepal.

Introduction:Hirayama disease (HD) is juvenile monomelic amyotrophy of the distal upper limb first described by Hirayama in 1959 AD. HD is a benign condition with chronic microcirculatory changes. The hallmark of HD is necrosis of the anterior horns of the distal cervical spine. Materials and Methods:Eighteen patients were assessed for clinical and radiological Hirayama disease. Clinical criteria included insidious onset nonprogressive chronic upper limb weakness and atrophy in teens or early twenties without sensory deficits and coarse tremors. MRI was done in a neutral position followed by neck flexion to evaluate cord atrophy and flattening, abnormal cervical curvature, loss of attachment between the posterior dural sac and subjacent lamina, anterior shifting of the posterior wall of the cervical dural canal, posterior epidural flow voids, and an enhancing epidural component with its dorsal extension. Results:The mean age was 20.33 years, and the majority, 17 (94.4%), were male. Neutral-position MRI revealed loss of cervical lordosis in 5 (27.8%) patients, cord flattening in all patients with asymmetry in 10 (55.5%), and cord atrophy was observed in 13 (72.2%) patients with localized cervical cord atrophy in only 2 (11.1%) and extension of atrophy to dorsal cord in 11 (61.1%) patients. Intramedullary cord signal change was seen in 7 (38.9%) patients. Loss of attachment of posterior dura and subjacent lamina and anterior displacement of dorsal dura was seen in all patients. A crescent-shaped epidural intense enhancement was noted along the posterior aspect of the distal cervical canal in all patients, with dorsal level extension in 16 (88.89%) patients. The mean thickness of this epidural space was 4.38 +/- 2.26 (mean +/- 2SD), and the mean extension was 5.5 +/- 4.6 vertebral levels (mean +/- 2SD). Conclusion:The high degree of clinical suspicion can guide additional contrast studies in flexion as a set MRI protocol for early detection and avoiding false negative diagnoses of HD.